Ultrasonic techniques have recently been introduced as methods free of ionizing radiation for non-invasive assessment of skeletal status in patients with osteoporosis. Quantitative aspects of these ultrasonic techniques can permit assessment of bone mass and density, as well as bone structure. Ultrasonic techniques for evaluating skeletal status also include measurements of speed of sound ("SOS") that reflect the transmission velocity of ultrasonic waves passing through bone tissue and soft tissue, measurements of broadband ultrasonic attenuation ("BUA") that assess the frequency dependence of ultrasonic attenuation, and pulse echo techniques that measure the energy scattered from the internal structure of the bone.
Many different measurement sites have been proposed for osteoporosis, such as the tibia, the patella, the phalanges, or the calcaneus. The calcaneus is preferred for quantitative ultrasonic measurements of skeletal status. It is composed of predominantly trabecular bone with only a thin cortical bone envelope medially and laterally which together provide an excellent medium for detecting changes in SOS and BUA measurements. The calcaneus also permits convenient ultrasonic interrogation for the operator and the patient alike.
Although a number of commercial devices exist for diagnosis of osteoporosis, clinicians have recognized the limitations of such devices and methods. Correlations between quantitative ultrasonic measurements and assessments of bone mineral density using quantitative computed tomography, dual x-ray absorptiometry, and single photon absorptiometry have been reported to be poor at the calcaneus, as well as at other sites.
Consequently, the inventors have recognized the need, among other things, to provide reliable ultrasonic devices and accurate, and qualitative or quantitative methods for ultrasonic measurements in the diagnosis of osteoporosis, as well as methods and devices to generally improve diagnostic tools based on ultrasonic measurements. The methods and devices provided herein permit, among other things, correction of ultrasonic parameters, such as speed of sound and broadband ultrasonic attenuation, for soft tissue interposed in the ultrasonic beam.